1. Field of the Invention
The present invention relates generally to networks, and more particularly to tracing paths of packets through a network.
2. Description of the Related Art
The industry is moving towards large layer-2 networks, using virtualized topologies such as fabrics, multi-chassis trunking (MCT) and virtual link aggregation groups (vLAG) to hide complexity. To debug these networks, the customer needs to uncover the complexity and trace the packet. However, this debugging is cumbersome and impractical today. This causes the customer to escalate the problems to the vendors. Studies have shown that very high percentages of these escalations involve packet loss and in each case the great majority of the time is spent identifying the culprit network node. Even for the vendors there is a lack of industry tools to easily debug layer-2 networks along the forwarding path as often multiple tools are needed to trace a single end-end layer-2 path. Indeed, there is no mechanism to locate layer-2 loops. The debugging is made more complicated because many problems have the same symptoms. Further, as the problems are present on production networks, no configuration changes can be done, there is live production background traffic and there is limited time to do the debugging.
Table 1 is a table of various debugging tools, their functionality and how specific situations are handled.
TABLE 1Debugging BUMBlackhole(Broadcast, Unicast,ToolsFunctionalityL2 LoopsscenariosMulticast) treeEthernet OAMLink-trace toLimitedCannot traceLimited(Operations,trace L2 path.forwardingAdministration,Mainly usedpath hashedand Maintenance)between SP's.based upon(802.1ag/CFMpacket headers(ConnectivityFaultManagement))Brocade L2LimitedVDX: N/AVDX: Edge-VDX: No supportTraceroutesupport forMLX: Limitedport forwardingMLX: Limitedtracing L2not validatedpacket path,MLX: Does notspecific to avalidateproduct lineforwardingpathCiscoCDP (CiscoLimitedDoes not verifyDoes not coverTraceroute macDiscoveryforwardingfloodingProtocol)pathscenariobased, does notapply to virtualnetworksACL, SPAN &Common tools,Operator shouldOperator shouldImpracticalinterfacebut cumbersomeknow theknow thein a failurestatisticsto trace packetproblematicproblematicscenariopathlink to capturelink to capturedatadataEdge LoopDetect loopsDetects, butMay detect loops,Flooding loopsDetectionbased upon itsdoes not locatebut does notdetect, but notreturnedlocatelocateheartbeat
Therefore it would be desirable to be able to more easily and completely debug packet flows in a network.